1. Field of the Invention
Embodiments of the present invention relate to deposition methods for forming thin films of metal compounds, such as metal oxides or metal nitrides, on substrates for use in manufacturing semiconductor devices, flat-panel display devices, and other electronic devices.
2. Description of the Related Art
In the field of semiconductor processing, flat-panel display processing or other electronic device processing, chemical vapor deposition (CVD) has played an important role in forming films on substrates. As the geometries of electronic devices continue to shrink and the density of devices continues to increase, the size and aspect ratio of the features are becoming more aggressive, e.g., feature sizes of 0.07 microns and aspect ratios of 10 or greater are contemplated. Accordingly, conformal deposition of materials to form these devices is necessary.
While conventional CVD has proven successful for device geometries and aspect ratios up to 0.15 microns, the more aggressive device geometries require new, innovative deposition techniques. Techniques that are receiving considerable attention include rapid cycle (pulsed) CVD and atomic layer deposition (ALD). In such schemes, reactants are introduced sequentially into a processing chamber where each reactant adsorbs onto the surface of the substrate where a surface reaction occurs. A purge step is typically carried out between the delivery of each reactant gas. The purge step may be a continuous purge with the reactant gases or a pulse purge between the delivery of the reactant gases.
Deposition of metal compounds from metal organic compounds typically results in trace amounts of carbon in the deposited film. The carbon is introduced into the film from the organic groups on the metal organic compound or a solvent such as toluene that may be added to assist in vaporizing the metal organic compound, or both. Although ALD enhances molecular reactions at the surface of the substrate between the metal organic precursors and reactive gases, the process temperatures and reaction times used for ALD typically do not reduce the carbon content below detectable limits. The residual carbon typically is an impurity that may migrate to surrounding layers.
U.S. Pat. No. 6,200,893, entitled “Radical-assisted Sequential CVD,” describes a method for CVD deposition on a substrate where radical species such as hydrogen and oxygen or hydrogen and nitrogen are introduced into a processing chamber in an alternating sequence with a precursor. Each compound, the radical species and the precursor, are adsorbed onto the substrate surface. The result of this process is two-fold; the components react with each other, as well as prepare the substrate surface with another layer of compound for the next step. By repeating the cycles, a film of desired thickness is produced. In a preferred embodiment the depositions from the molecular precursor are metals, and the radicals in the alternate steps are used to remove ligands left from the metal precursor reactions, as well as to oxidize or nitridize the metal surface in subsequent layers. However, the reference does not address removal of carbon from metal compounds produced from metal organic compounds.
Therefore, there is a need for a process for depositing metal compounds such as metal oxides and metal nitrides from metal organic compounds to provide thin films that do not have detectable carbon.